Pilot scrambling enabling direct pilot sequence detection in initial acquisition in evolved UTRA

ABSTRACT

A communications network and method thereof include a base station controller configured to provide a repetition period of a primary synchronization channel to be equal to a predetermined integer value times a scrambling code length of the scrambling code of a common pilot channel. A user equipment in the network is configured to search for a known sequence comprising the primary synchronization channel to select a cell and a corresponding sub-frame/symbol timing from the selected cell.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/542,104, filed Oct. 4, 2006, which in turn claims priority to U.S.Provisional Patent Application Ser. No. 60/730,867, filed Oct. 28, 2006.The subject matter of these earlier filed applications are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is related to a design and arrangement of a Common PilotChannel (CPICH) and a Primary Synchronization Channel (P-SCH) in EvolvedUniversal Mobile Telecommunications System Terrestrial Radio Access(UTRA).

2. Description of the Related Art

A mobile station (or wireless device) routinely performs a cell search(or synchronization) function to detect and acquire the base stations ofa wireless network in the vicinity of the wireless device. Fastdetection of the base stations is critical to the performance of boththe mobile station and the wireless network, particularly in the new3^(rd) Generation Partnership Project (3GPP) Evolved UTRA wirelesssystem. Fast detection of base stations allows a mobile station toaccess a wireless network more rapidly, for instance, by reducingacquisition delay. Fast detection of base stations also enables themobile station and the wireless network to perform faster handoffsbetween base station cell sites or between sectors of the same basetransceiver subsystem (BTS) of a base station. Additionally, fastdetection reduces the number of calls that are dropped during thehandoff process.

Correlation procedures are used for a wide range of tasks in a mobileradio receiver. For instance, a receiver receives a signal includingdata. In a correlation process, the data is compared, in the form ofsample values, with a sequence of data items, which are known in thereceiver. If the arriving data matches the sequence of known data, acorrelation signal is emitted which indicates that the sequence of knowndata items has been identified in the received signal.

By way of example, time-slot synchronization in the receiver is carriedout on the basis of the correlation of a pilot signal with a pilotsequence which is known in the receiver. In a Universal MobileTelecommunications System (UMTS) Standard, the synchronization signalfor the time-slot synchronization is transmitted via a P-SCH (PrimarySynchronization Channel). A synchronization sequence, which is known inthe receiver, has a length of 256-chip codeword, and is transmitted at astart of each time slot.

Frame synchronization is likewise carried out by correlation of atransmitted pilot signal with a known pilot sequence. In the UMTSStandard, the code sequence for frame synchronization and code groupacquisition is transmitted via a S-SCH (Secondary SynchronizationChannel). The spreading factor for the second code sequence is likewise256 chips. A third example of the use of correlation procedures forcarrying out a mobile radio task relates to an estimation of a delaytime for one transmitted signal propagation path. Owing to multipathpropagation in mobile radio systems, one and the same transmitted signalis received with a time offset at the receiver, and with differentattenuation levels, via different propagation paths. In the course of anequalization process, the time offset between the individual signalcomponents must be measured and must be compensated for using, forinstance, delay estimation. The estimation of the delay time on thepropagation path, which is also referred to as delay estimation, iscarried out using a product correlation sequence comprising a scramblingcode, a channelization code, and pilot symbols.

The time-slot and frame synchronizations are used to search for new(mobile radio) cells in the so-called active set (group of currentlyused cells) and in a so-called monitor set (group of monitored cellswhich are candidates for the active set). Time-slot and framesynchronizations must, therefore, be carried out continually even whentelephone connection has already been set up. An analogous procedureapplies, of course, for delay estimation, which must be continuallyupdated on the basis of changing channel conditions.

A Common Pilot Channel (CPICH) code can be detected directly afterPrimary Synchronization Channel (P-SCH) detection by correlating allpossible pilot sequences with received CPICH. However, the complexity ofthat procedure may be high due to a long scrambling code (compared tothe repetition period of the P-SCH) of, for instance, 10 ms. Thisimplies that, a user equipment (UE) has to deal with the uncertainty ofboth the scrambling code number and the phase of the scrambling code,which either increases the complexity of the UE or increases the CPICHsearch time.

In another conventional system, an intermediate step is added betweenthe P-SCH and CPICH detection which uses a Secondary SynchronizationChannel (S-SCH). However, conventional systems do no allow for arrangingthe P-SCH and CPICH in order to make CPICH detection with as much lowimplementation complexity as possible. A system and method are neededthat would allow cell specific scrambling of the CPICH to be appliedwithout the need for the S-SCH.

SUMMARY OF THE INVENTION

In accordance with an embodiment of the present invention, there isprovided a communications network, including a network elementconfigured to provide a repetition period of a primary synchronizationchannel to be equal to a predetermined integer value times a scramblingcode length of a scrambling code of a common pilot channel, and a userequipment configured to search for a known sequence including theprimary synchronization channel to select a cell and a correspondingsub-frame/symbol timing from the selected cell.

In accordance with an embodiment of the present invention, there isprovided a communications network, including network element means forproviding a repetition period of a primary synchronization channel to beequal to a predetermined integer value times a scrambling code length ofa scrambling code of a common pilot channel, and user equipment meansfor searching for a known sequence including the primary synchronizationchannel to select a cell and a corresponding sub-frame/symbol timingfrom the selected cell.

In accordance with an embodiment of the present invention, there isprovided a network element in a cell site, including a controllerconfigured to generate a repetition period of a primary synchronizationchannel to be equal to a predetermined integer value times a scramblingcode length of a scrambling code of a common pilot channel, and atransmitter configured to output the primary synchronization channelwith the repetition period to a user equipment.

In accordance with an embodiment of the present invention, there isprovided a network element in a cell site, including controller meansfor generating a repetition period of a primary synchronization channelto be equal to a predetermined integer value times a scrambling codelength of a scrambling code of a common pilot channel, and transmittermeans for outputting the primary synchronization channel with therepetition period to a user equipment.

In accordance with an embodiment of the present invention, there isprovided a user equipment in a cell site, including a first selectorconfigured to select a carrier frequency candidate from a set of carrierfrequencies, a search unit configured to search for a known sequenceincluding a primary synchronization channel received from a networkelement, and a second selector configured to select a cell and acorresponding sub-frame/symbol timing based on the search for the knownsequence.

In accordance with an embodiment of the present invention, there isprovided a user equipment in a cell site, including first selector meansfor selecting a carrier frequency candidate from a set of carrierfrequencies, search means for searching for a known sequence including aprimary synchronization channel received from a network element, andsecond selector means for selecting a cell and a correspondingsub-frame/symbol timing based on the search for the known sequence.

In accordance with an embodiment of the present invention, there isprovided a method and a computer program embodied on a computer readablemedium of a communications network, including providing a repetitionperiod of a primary synchronization channel to be equal to apredetermined integer value times a scrambling code length of ascrambling code of a common pilot channel, searching for a knownsequence including the primary synchronization channel, and selecting acell and a corresponding sub-frame/symbol timing from the selected cell.

In accordance with an embodiment of the present invention, there isprovided a method and a computer program embodied on a computer readablemedium of a network element in a cell site, including generating arepetition period of a primary synchronization channel to be equal to apredetermined integer value times a scrambling code length of ascrambling code of a common pilot channel, and outputting the primarysynchronization channel with the repetition period to a user equipment.

In accordance with an embodiment of the present invention, there isprovided a method and a computer program embodied on a computer readablemedium of a user equipment in a cell site, including selecting a carrierfrequency candidate from a set of carrier frequencies, searching for aknown sequence including a primary synchronization channel received froma network element, and selecting a cell and a correspondingsub-frame/symbol timing based on the searching for the known sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments, details, advantages and modifications of thepresent invention will become apparent from the following detaileddescription of the preferred embodiments which is to be taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates an exemplary wireless network, in accordance with anembodiment of the present invention;

FIG. 2 a structure of a frame, in accordance with an embodiment of thepresent invention;

FIG. 3 illustrates an exemplary primary synchronization channel (P-SCH),in accordance with an embodiment of the present invention;

FIG. 4 illustrates a method for a common control pilot channel (CPICH)scrambling code design for different bandwidths, in accordance with anembodiment of the present invention;

FIG. 5 illustrates a base station and a user equipment or mobile stationin a wireless communication network, in accordance with an embodiment ofthe present invention; and

FIG. 6 illustrates a cell search method, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with an embodiment of the present invention, there isprovided a system and method in which a Common Pilot Channel (CPICH) anda Primary Synchronization Channel (P-SCH) are arranged in Evolved UTRA,being standardized under 3GPP UTRA Long Term Evolution. P-SCH is mainlyused for cell search purposes, which is primarily initial cell search,but also neighbor cell synchronization prior to handover measurements.The Primary Synchronization Channel (P-SCH) may be also referred to as aCommon Synchronization Channel in 3GPP. The main purpose of the Commonpilot channel (CPICH) is to perform a channel estimation which is abasic measurement for any detection algorithm. The Common pilot channel(CPICH) may also be referred to as Reference Symbols in 3GPP. Also,Scrambling Code may be referred as Pilot Sequence in 3GPP.

In one embodiment, the present invention relates to E-UTRA (EvolvedUniversal Mobile Telecommunications System Terrestrial Radio Access)systems, currently being evaluated and standardized for the long termevolution of Wideband Code Division Multiple Access (WCDMA) technology.In accordance with an embodiment of the present invention, a system anda method of the present invention are configured to arrange the P-SCHand the CPICH, in order to perform CPICH detection with as lowimplementation complexity as possible. In one embodiment, the cellspecific scrambling of the CPICH may be applied without the need for aSecondary Synchronization Channel (S-SCH).

FIG. 1 illustrates exemplary a wireless network 100, in accordance withan embodiment of the present invention. The wireless network 100comprises a plurality of cell sites 121, 122, and 123, each containing abase station (BS) 101, BS 102, and BS 103, respectively. BS 101 and 103communicate with mobile stations (MS) 111 and 114 over channelsaccording to the Evolved UTRA. The MS 111 and 114 may be any suitableuser equipment or wireless device, including conventional cellularradiotelephones, PCS handset devices, personal digital assistants,portable computers, or metering devices. A person of ordinary skill inthe art will appreciate that other types of access terminals other thanmobile devices may be used, including fixed wireless terminals.

Dotted lines show the approximate boundaries of the cell sites 121, 122,and 123 in which base stations 101, 102, and 103 are located. The cellsites are shown approximately circular for the purposes of illustrationand explanation only. A person of ordinary skill in the art willappreciate that the cell sites often have other irregular shapes,depending on the cell configuration selected and natural and man-madeobstructions.

As is well known in the art, cell sites 121, 122, and 123 include aplurality of sectors (not shown), each being illuminated by adirectional antenna coupled to the base station. The embodiment of FIG.1 illustrates the BSs 101, 102, and 103 in the center of eachcorresponding cell. Alternate embodiments position the directionalantennas in corners of the sectors. The system of the present inventionis not limited to any particular cell site configuration.

In one embodiment of the present invention, BS 101, BS 102, and BS 103each may include a base station controller (BSC) and one or more basetransceiver subsystem(s) (BTS). The BSC and the BTS subsystems are wellknown to those skilled in the art. The BSC is a device that manageswireless communications resources, including the base transceiverstations, for specified cells within a wireless communications network.The BTS comprises the RF transceivers, antennas, and other electricalequipment located in each cell site.

BS 101, BS 102 and BS 103 transfer voice and data signals between eachother and the public switched telephone network (PSTN) (not shown) andthe Internet via communication line 131, mobile switching center (MSC)140, and packet data serving node (PDSN) 150. MSC 140 is a switchingdevice that provides services and coordination between the subscribersin a wireless network and external networks, such as the PSTN orInternet. BS 101, BS 102 and BS 103 transmit or send signals to MS 111and 114 over channels according to the Evolved UTRA. The signal mayinclude a Primary-Synchronization Channel (P-SCH) and/or a scramblingcode of the common pilot channel (CPICH). The scrambling code or thescrambling code of the CPICH may also be referred to as a pilotsequence.

In the exemplary wireless network 100, MS 111 is located in cell site121 and is in communication with BS 101. MS 113 is located in cell site122 and is in communication with BS 102. MS 114 is located in cell site123 and is in communication with BS 103. MS 112 is also located close tothe edge of cell site 123 and is moving in the direction of cell site123, as indicated by the direction arrow proximate MS 112. At somepoint, as MS 112 moves into cell site 123 and out of cell site 121, ahand-off will occur.

Evolved UTRA is a system with frequency re-use=1, that is, several cellsare transmitting at the same carrier frequency. In the Evolved UTRA, auser equipment (UE) or a mobile station (MS) must acquire the best cellwith the minimum path loss between the cell and the target UE or MS.This initial cell acquisition process is called cell search.Accordingly, the pilot sequence of CPICH has to be scrambled by cellspecific scrambling code in order to ensure good channel estimation inthe presence of inter-cell interference. Furthermore, the pilotscrambling code uniquely identifies the BS.

Accordingly, for initial cell search, the MS 111 or 114 searches througha set of potential carrier frequencies. For a certain carrier frequencycandidate, the MS 111 or 114 searches for a known sequence (P-SCH), inorder to select a cell, and select the corresponding subsub-frame/symboltiming from the selected cell. The cell is then identified by detectinga cell specific sequence of pilot symbols, i.e., the CPICH, transmittedby the wireless network 100. CPICH detection should be possible with areasonable amount of computing. The computing needs are determined bythe amount of available possibilities that should be tried out.

Thus, each one of MS 111 and 114 routinely performs cell searches todetect the base stations of a wireless network in the vicinity of themobile stations. Whenever one of MS 111 and 114 is turned on, an initialcell search is performed in order to search for and acquire at least oneof base stations 101 and 103 of wireless network 100. Thereafter, eachMS 111 and 114 continues to perform cell searches in order to determinethe strongest base station(s) in the vicinity and to identify availablebase stations to which the mobile station may be transferred in case itis necessary to perform a handoff. To improve the efficiency of thesecell searches, the present invention provides a base station controller(e.g., BS 110, 102, 103) configured to align a length of scrambling codeof CPICH with a repetition period of the P-SCH. In accordance with anembodiment of the present invention, the repetition period of the P-SCHmay be equal to a predetermined value, such as an integer, times thescrambling code length of the CPICH.

The present invention assumes that P-SCH is located at a fixed symbolposition within a sub-frame and that this sub-frame containing the P-SCHis repeated with a fixed period. In one embodiment, the P-SCH is thelast symbol of the sub-frame and it is repeated in every 5th sub-frame.A frame of, for instance, 10 ms, may include 20 sub-frames of 0.5 ms.The sub-frame may include seven symbols. Thus, as illustrated in FIG. 2,the 4.sup.th sub-frame, the 9.sup.th sub-frame, the 14sub-frame, and the19.sup.th sub-frame include the P-SCH as the last symbol. According toan embodiment of the present invention, the CPICH scrambling code maystart with a fixed time offset relative to the P-SCH. In one example,the CPICH scrambling code may start in the first symbol of the nextsub-frame after P-SCH (see FIG. 3). Thus, the phase of the scramblingcode is known and, therefore, the UE CPICH detection algorithm wouldonly identify which cell specific scrambling code that is applied.

In one example, as illustrated in FIG. 3, the P-SCH may be transmittedat a lowest bandwidth of, for instance, 1.25 MHz. During initialsynchronization, the P-SCH is searched, for instance by correlating thereceived signal with a local time-domain replica of the P-SCH andselecting the timing with maximum power of the correlation results.Based on the found P-SCH, the position of the symbol in the sub-framewith the CPICH can be determined, as well as the phase of the scramblingcode, due to the unambiguous relation between P-SCH timing and the CPICHscrambling code phase. In an exemplary embodiment, the P-SCH is alwaystransmitted in the lowest bandwidth (e.g. 1.25 MHz) despite the deployedbandwidth, and the CPICH scrambling code is arranged so that the center1.25 MHz frequency part is always the same for all deploymentbandwidths, as depicted in FIG. 4. Therefore, if the mobile station isconfigured to the minimum bandwidth (e.g. 1.25 MHz) then the P-SCH and acenter part of CPICH detection may be done without knowing the operatingbandwidth of the network. The CPICH detection may be performed bycorrelating (in time or frequency domain) the incoming received signalat pilot symbol locations with local replicas of all or a set of theCPICH scrambling codes. The scrambling code that maximizes the power ofthe correlation is selected as the estimate of the CPICH scrambling codeapplied. FIG. 4 illustrates the CPICH scrambling code arrangement fordifferent bandwidths, in accordance with an embodiment of the presentinvention.

FIG. 5 illustrates a base station 180 and a user equipment or mobilestation 186 in a wireless communication network, in accordance with anembodiment of the present invention, performing the functions describedabove. The base station 180 may include a base station controller 182and one or more base transceiver subsystem(s) 184. The base stationcontroller 182 may also provide a repetition period of the P-SCH to beequal to a predetermined value, such as an integer, times the scramblingcode length of the CPICH. The base station controller 182 would alsoalign a length of scrambling code of the CPICH with the repetitionperiod of the P-SCH. The base station controller 182 may be furtherconfigured to provide a cell specific sequence of pilot symbols of thecommon pilot channel, i.e. the common pilot channel is scrambled by acell specific scrambling code. The base transceiver subsystem(s) 184 maybe configured to output the P-SCH with a certain repetition period tothe user equipment 186.

A first selector 188 in the user equipment 186 may be configured toselect a carrier frequency candidate from a set of carrier frequencies,and a search unit 190 would be configured to search for the knownsequence including the P-SCH received from the base transceiversubsystem(s) 184 in the base station 180. A second selector 192 may beconfigured to select the cell and a corresponding sub-frame/symboltiming based on the search, and, based on the scrambling by thescrambling code of the CPICH, an identifying unit 194 may be configuredto identify the selected cell by detecting the cell specific sequence ofpilot symbols of the CPICH (scrambling code). The identifying unit 194may be configured to identify the cell specific scrambling code of thecommon pilot channel based on search results derived from the P-SCHonly, the S-SCH only, or both the P-SCH and the S-SCH.

FIG. 6 illustrates a cell search method, in accordance with anembodiment of the present invention. At step 200, a carrier frequencycandidate is selected. At step 210, a search is performed for a knownsequence. At step 220, a cell and the corresponding symbol/sub-frametiming are selected. At step 230, the selected cell is identified.

It is to be understood that in the embodiment of the present invention,the operations are performed in the sequence and manner as shownalthough the order of some operations and the like may be changedwithout departing from the spirit and scope of the present invention.

The steps of a method or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

With respect to the present invention, network elements may be anydevice that utilizes network data, and can include switches, routers,bridges, gateways or servers. In addition, white the terms packet anddatagram have been used in the description of the present invention, theinvention has import to many types of network data. For purposes of thisinvention, the term data includes packet, cell, frame, datagram, bridgeprotocol data unit packet, packet data, and any equivalents thereof.

One having ordinary skill in the art will readily understand that theinvention as discussed above may be practiced with steps in a differentorder, and/or with hardware elements in configurations which aredifferent than those which are disclosed. Therefore, although theinvention has been described based upon these preferred embodiments, itwould be apparent to those of skill in the art that certainmodifications, variations, and alternative constructions would beapparent, while remaining within the spirit and scope of the invention.

1. A communications network, comprising: a network element configured toprovide a repetition period of a primary synchronization channel to beequal to a predetermined integer value times a scrambling code length ofa scrambling code of a common pilot channel; and a user equipmentconfigured to search for a known sequence comprising the primarysynchronization channel to select a cell and a correspondingsubframe/symbol timing from the selected cell.
 2. The network as recitedin claim 1, wherein the network element is further configured to use thescrambling code to scramble the common pilot channel to provide a cellspecific sequence of pilot symbols of the common pilot channel.
 3. Thenetwork as recited in claim 2, wherein the user equipment furthercomprises: an identifying unit configured to identify the selected cellby detecting the cell specific sequence of pilot symbols.
 4. The networkas recited in claim 3, wherein the identifying unit is furtherconfigured to apply the cell specific scrambling of the common pilotchannel.
 5. The network as recited in claim 1, wherein the networkelement is further configured to align a length of scrambling code of acommon pilot channel with a repetition period of the primarysynchronization channel.
 6. A communications network, comprising:network element means for providing a repetition period of a primarysynchronization channel to be equal to a predetermined integer valuetimes a scrambling code length of a scrambling code of a common pilotchannel; and user equipment means for searching for a known sequencecomprising the primary synchronization channel to select a cell and acorresponding subframe/symbol timing from the selected cell.
 7. Thenetwork as recited in claim 6, wherein the network element means furtheruses the scrambling code to scramble the common pilot channel forproviding a cell specific sequence of pilot symbols of the common pilotchannel.
 8. The network as recited in claim 7, wherein the userequipment means further comprises: identifying means for identifying theselected cell by detecting the cell specific sequence of pilot symbols.9. The network as recited in claim 8, wherein the identifying meansapplies the cell specific scrambling of the common pilot channel. 10.The network as recited in claim 6, wherein the network element meansaligns a length of scrambling code of a common pilot channel with arepetition period of the primary synchronization channel.
 11. A networkelement, comprising: a controller configured to generate a repetitionperiod of a primary synchronization channel to be equal to apredetermined integer value times a scrambling code length of ascrambling code of a common pilot channel; and a transmitter configuredto output the primary synchronization channel with the repetition periodto a user equipment.
 12. The network element as recited in claim 11,wherein the controller is further configured to use the scrambling codeto scramble the common pilot channel to provide a cell specific sequenceof pilot symbols of the common pilot channel.
 13. The network element asrecited in claim 11, wherein the controller is further configured toalign a length of scrambling code of a common pilot channel with arepetition period of the primary synchronization channel.
 14. Thenetwork element as recited in claim 11, wherein the controller comprisesa base station controller and the transmitter comprises Radio Frequencytransceivers, antennas, and other electrical equipment located in eachcell site.
 15. A network element, comprising: controller means forgenerating a repetition period of a primary synchronization channel tobe equal to a predetermined integer value times a scrambling code lengthof a scrambling code of a common pilot channel; and transmitter meansfor outputting the primary synchronization channel with the repetitionperiod to a user equipment.
 16. A method of a communications network,comprising: providing a repetition period of a primary synchronizationchannel to be equal to a predetermined integer value times a scramblingcode length of a scrambling code of a common pilot channel; searchingfor a known sequence comprising the primary synchronization channel; andselecting a cell and a corresponding sub-frame/symbol timing from theselected cell.
 17. The method as recited in claim 16, furthercomprising: using the scrambling code to scramble the common pilotchannel to provide a cell specific sequence of pilot symbols of thecommon pilot channel.
 18. The method as recited in claim 17, furthercomprising: identifying the selected cell by detecting the cell specificsequence of pilot symbols.
 19. The method as recited in claim 17,further comprising: aligning a length of scrambling code of a commonpilot channel with a repetition period of the primary synchronizationchannel.
 20. A method of a network element in a cell site, comprising:generating a repetition period of a primary synchronization channel tobe equal to a predetermined integer value times a scrambling code lengthof a scrambling code of a common pilot channel; and outputting theprimary synchronization channel with the repetition period to a userequipment.
 21. The method as recited in claim 20, further comprising:using the scrambling code to scramble the common pilot channel toprovide a cell specific sequence of pilot symbols of the common pilotchannel.
 22. The method as recited in claim 20, further comprising:aligning a length of scrambling code of a common pilot channel with arepetition period of the primary synchronization channel.
 23. A computerprogram embodied on a computer readable medium of a wirelesscommunication network, the computer program being configured to perform:providing a repetition period of a primary synchronization channel to beequal to a predetermined integer value times a scrambling code length ofa scrambling code of a common pilot channel; searching for a knownsequence comprising the primary synchronization channel; and selecting acell and a corresponding sub-frame/symbol timing from the selected cell.24. The computer program as recited in claim 23, further comprising:using the scrambling code to scramble the common pilot channel toprovide a cell specific sequence of pilot symbols of the common pilotchannel.
 25. The computer program as recited in claim 24, furthercomprising: identifying the selected cell by detecting the cell specificsequence of pilot symbols.
 26. The computer program as recited in claim24, further comprising: aligning a length of scrambling code of a commonpilot channel with a repetition period of the primary synchronizationchannel.
 27. A computer program embodied on a computer readable mediumof a network element in a cell site, the computer program beingconfigured to perform: generating a repetition period of a primarysynchronization channel to be equal to a predetermined integer valuetimes a scrambling code length of a scrambling code of a common pilotchannel; and outputting the primary synchronization channel with therepetition period to a user equipment.
 28. The computer program asrecited in claim 27, further comprising: using the scrambling code toscramble the common pilot channel to provide a cell specific sequence ofpilot symbols of the common pilot channel.
 29. The computer program asrecited in claim 27, further comprising: aligning a length of scramblingcode of a common pilot channel with a repetition period of the primarysynchronization channel.
 30. The network as recited in claim 1, whereinthe predetermined integer value is
 1. 31. The network as recited inclaim 3, wherein the identifying unit is further configured to identifythe cell specific scrambling code of the common pilot channel based onsearch results derived only from the primary synchronization channel.32. The network as recited in claim 3, wherein the identifying unit isfurther configured to identify the cell specific scrambling code of thecommon pilot channel based on search results derived from the primarysynchronization channel and without deriving information from asecondary synchronization channel.
 33. The network as recited in claim4, wherein the identifying unit applies the cell specific scrambling ofthe common pilot channel without the need for a secondarysynchronization channel.
 34. The network as recited in claim 6, whereinthe predetermined integer value is
 1. 35. The network as recited inclaim 8, wherein the identifying means identifies the cell specificscrambling code of the common pilot channel based on search resultsderived only from the primary synchronization channel.
 36. The networkas recited in claim 8, wherein the identifying means identifies the cellspecific scrambling code of the common pilot channel based on searchresults derived from the primary synchronization channel and withoutderiving information from a secondary synchronization channel.
 37. Thenetwork as recited in claim 9, wherein the identifying means applies thecell specific scrambling of the common pilot channel without the needfor a secondary synchronization channel.
 38. The network element asrecited in claim 11, wherein the predetermined integer value is
 1. 39.The network element as recited in claim 15, wherein the predeterminedinteger value is
 1. 40. The network element as recited in claim 15,wherein the controller means uses the scrambling code to scramble thecommon pilot channel to provide a cell specific sequence of pilotsymbols of the common pilot channel.
 41. The network element as recitedin claim 15, wherein the controller means aligns a length of scramblingcode of a common pilot channel with a repetition period of the primarysynchronization channel.
 42. The method as recited in claim 16, whereinthe predetermined integer value is
 1. 43. The method as recited in claim18, wherein identifying the selected cell comprises identifying the cellspecific scrambling code of the common pilot channel based on searchresults derived only from the primary synchronization channel.
 44. Themethod as recited in claim 18, wherein identifying the selected cellcomprises identifying the cell specific scrambling code of the commonpilot channel based on search results derived from the primarysynchronization channel and without deriving information from asecondary synchronization channel.
 45. The method as recited in claim18, wherein identifying the selected cell comprises applying the cellspecific scrambling of the common pilot channel without the need for asecondary synchronization channel.
 46. The method as recited in claim20, wherein the predetermined integer value is
 1. 47. The computerprogram as recited in claim 23, wherein the predetermined integer valueis
 1. 48. The computer program as recited in claim 25, whereinidentifying the selected cell comprises identifying the cell specificscrambling code of the common pilot channel based on search resultsderived only from the primary synchronization channel.
 49. The computerprogram as recited in claim 25, wherein identifying the selected cellcomprises identifying the cell specific scrambling code of the commonpilot channel based on search results derived from the primarysynchronization channel and without deriving information from asecondary synchronization channel.
 50. The computer program as recitedin claim 25, wherein identifying the selected cell comprises applyingthe cell specific scrambling of the common pilot channel without theneed for a secondary synchronization channel.
 51. The computer programas recited in claim 27, wherein the predetermined integer value is 1.52. A network element, comprising: a controller configured to offset astart time of a scrambling code of a common pilot channel by a fixedtime relative to a primary synchronization channel; and a transmitterconfigured to output the primary synchronization channel and thescrambling code of the common pilot channel to a user equipment.
 53. Anetwork element, comprising: controller means for offsetting a starttime of a scrambling code of a common pilot channel by a fixed timerelative to a primary synchronization channel; and transmitter means foroutputting the primary synchronization channel and the scrambling codeof the common pilot channel to a user equipment.
 54. A method of acommunications network, comprising: offsetting a start time of ascrambling code of a common pilot channel by a fixed time relative to aprimary synchronization channel; and outputting the primarysynchronization channel and the scrambling code of the common pilotchannel to a user equipment.
 55. A computer program embodied on acomputer readable medium of a network element in a cell site, thecomputer program being configured to perform: offsetting a start time ofa scrambling code of a common pilot channel by a fixed time relative toa primary synchronization channel; and outputting the primarysynchronization channel and the scrambling code of the common pilotchannel to a user equipment.